NSTextLists not rendered when NSTextContentStorageDelegate textContentStorage (_:, textParagraphWith:) is implemented

I have a UITextView that contains paragraphs with text bullet lists (via NSTextList). I also implement NSTextContentStorageDelegate.textContentStorage(_:, textParagraphWith:) in order to apply some custom attributes to the text without affecting the underlying attributed text. My implementation returns a new NSParagraph that modifies the foreground color of the text. I based this on the example in the WWDC 21 session "Meet Text Kit 2".

UITextView stops rendering the bullets when I implement the delegate function and return a custom paragraph. Why?

func textContentStorage(_ textContentStorage: NSTextContentStorage, textParagraphWith range: NSRange) -> NSTextParagraph? {
    guard let originalText = textContentStorage.textStorage?.attributedSubstring(from: range) else { return nil }

    let updatedText = NSMutableAttributedString(attributedString: originalText)
    updatedText.addAttribute(.foregroundColor, value: UIColor.green, range: NSRange(location: 0, length: updatedText.length))

    let paragraph = NSTextParagraph(attributedString: updatedText)

    // Verify that the text still contains NSTextList
    if let paragraphStyle = paragraph.attributedString.attribute(.paragraphStyle, at: 0, effectiveRange: nil) as? NSParagraphStyle {
        assert(!paragraphStyle.textLists.isEmpty)
    } else {
        assertionFailure("Paragraph has lost its text lists")
    }

    return paragraph
}